HIV Strains’ Resistance to Drugs on Rise
As many as one of every seven Americans who are newly infected by the AIDS virus carry a strain that is resistant to at least one of the drugs now used to treat the infections, San Diego researchers said Tuesday.
That represents a sharp increase from earlier studies and could have a major impact on treatment efforts. HIV-positive people with a resistant strain “are less likely to suppress virus replication with therapy, take longer to suppress the virus and have a shorter time to therapy failure,” Dr. Susan Little of UC San Diego said at the eighth annual Retrovirus Conference here.
The federal government, meanwhile, hopes to break the back of the AIDS epidemic with a program designed to cut the number of new HIV infections every year in half--from 40,000 to 20,000.
The $300-million program announced Tuesday by the Centers for Disease Control and Prevention is focused on identifying people who are newly infected by the virus but do not yet know it and thus present the greatest risk of transmitting it to others.
Most of CDC’s current prevention efforts are focused on trying to reduce risky behavior among the uninfected and those who already know they are infected, a program that costs about $600 million a year.
“We have been dealing with half the equation,” Dr. Robert Janssen of the CDC told a news conference announcing the program. “Now it is time to look at all of it. . . . It is critical that people learn they are infected.”
Resistance to AIDS drugs has always been a problem because of HIV’s ability to mutate under the stress of therapy, necessitating the use of ever more powerful drugs to fight infections. But those resistant viruses have in the past stayed in the patients where the resistance developed. Researchers have believed that drug-resistant strains could not be transmitted from person to person as easily as nonresistant strains, but the new results seem to refute that.
Little’s results came from a program in which new infections were monitored in nine cities, including Los Angeles. Patients were identified when they came into one of the participating clinics with a flu-like illness--caused by the rapid proliferation and high levels of virus in a new HIV infection--soon after a high-risk sexual contact or intravenous drug use.
About 10% of those infected with HIV develop such symptoms, which usually pass if left untreated, but all can readily transmit the virus because of their high viral levels.
The 394 patients in the study were diagnosed, on average, three months after infection. None had received any anti-HIV therapy.
Fourteen percent of the patients showed a tenfold reduction in susceptibility to at least one class of anti-HIV drugs during 1999 and early 2000, Little told the meeting. From 1995 to 1998, the corresponding figure was only 3.5%, indicating that there has been a sharp increase in resistance.
Likewise, during the last two years, the proportion who were resistant to two or more classes of drugs rose from 0.4% to 5.8%.
In a separate presentation, researchers from Harvard and Boston University reported that 18% of 88 newly diagnosed patients in Boston were resistant to at least one class of drugs and that 12% were resistant to at least two. They had no historical data to document an increase, however.
Studies from Switzerland and France also presented Tuesday showed a trend similar to Little’s data, suggesting that transmission of resistant viruses is a growing problem everywhere.
The more alarming findings came when the patients were treated with standard cocktails of three or more drugs, Little said. The results of such treatment showed that resistance to one drug limits the utility of all classes of drugs, she said.
Little recommended that all newly diagnosed HIV-positive people be tested for the presence of resistant strains and that therapeutic regimens be tailored to avoid use of drugs to which the virus is already less susceptible. But the high cost of the tests, which can run from $400 to $750, may limit the number of patients who can be screened, she conceded.
The increasing transmission of resistant viruses, Little added, is probably because more people are being treated than ever before.
When more people are treated, more develop resistance--which increases the likelihood of transmitting a resistant virus.
Regardless of whether the newly infected have a resistant strain, it is critical to identify them as soon as possible, the CDC’s Janssen said. Several studies have shown that people who become aware that they are HIV-positive reduce risky behaviors, increasing condom use and even refraining from sex more often.
But of the estimated 900,000 Americans who are HIV-positive, as many as 250,000 do not know it, the CDC says. The new effort, called Serostatus Approach to Fighting the HIV Epidemic, is designed to reduce that proportion.
A key ingredient of the new program is access to rapid HIV tests now being evaluated by the Food and Drug Administration. The tests, which use a drop of blood or saliva, can produce a result in as little as 15 minutes. Marketing of the tests has been delayed because of doubts about their reliability, but the CDC is clearly trying to encourage the FDA to make them available.
Such tests could be used in bars, bathhouses and other meeting places for people who engage in high-risk behavior. The CDC also argues that they should be given routinely--albeit voluntarily--to anyone who visits a hospital emergency room or enters jail.
To support that effort, the CDC is organizing a new media effort called Know Now to encourage testing. It will involve radio and bus ads aimed at neighborhoods where HIV is most likely to occur, and will be tested initially in Detroit, Houston, Miami, New Orleans and Jackson, Miss.
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